One prior method of producing thin, relatively defect free, monocrystalline structures, the Czochralski method, involves drawing a larger solid single crystal body known as a boule from a melt and then slicing the boule with a diamond saw, grinding and polishing it to produce wafers of thin, single crystal material. This process is slow, wasteful, and expensive and is used principally for the production of substrates in the electronics industry. Another method of growing single crystal structures, known as the EFG method (Edge defined, Filmfed, Growth), has found use in the manufacture of solar cells, EPROM windows, and abrasion-resistant plates. A considerable amount of effort has been expended on these two methods with the objective of finding an improved way to produce monocrystalline structures which need not be ground and polished to become useable as windows or substrates for electronic or optical applications. As yet, no satisfactory solution has been found.
Problems arise with the EFG method because of the inability to control flow dynamics and heat dissipation closely enough to prevent the formation of ripples in the crystal structure when it is being pulled from the melt. More particularly, as the crystal is being formed, the locus of solidification of the viscous melt material shifts slightly when the heat dissipation is even minutely retarded. This causes variations in the solidification of the molten mass which, in turn, produce surface unevenness, variations in thickness, and internal growth defects. These problems become more critical as the mass becomes thinner, reaching a point at which the subsequent grinding and polishing required to finish the crystal would fracture the crystal.
Thus, all present crystal forming techniques produce crystal structures whose attainable thinnesses are limited by the mechanical forces required to create final products with smooth, defect free surfaces. Because of this limit in achievable thinness, the single crystal plates and wafers which can be produced by prior methods are still essentially rigid and incapable of being flexed or wound up like ribbons without causing excessive breakage. Indeed, because of their stiffnesses, these crystals have never been considered for use as flexible, elastic members in the optics and electronics industries.
Other problems with crystal structures made by the above known methods stem from the great number of dislocations and irregularities present in the crystal lattices and from contamination by silicon carbide particles from the die or saw used when the crystal is cut into wafers. These dislocations and defects constitute impurities and irregularities in the crystal structure which contribute to breakage and poor yield when additional material layers or coatings are deposited onto the wafer surfaces; they are particularly important if other crystalline layers such as microcircuits are to be grown on the wafers.
Finally, none of the prior techniques enables the making of a uniformly thin, highly flexible monocrystalline web or film which can, with or without grinding and polishing, form a base or foundation for one or more added-on layers, patterns, or coatings to form a composite structure having a coherent crystal morphology throughout all layers.